<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	
</body>
</html>
<script>
	Person.prototype = String.prototype;
	function Person(){

	} 
	String.prototype.a = 20;
	Person.prototype.a = 30;
	var p = new Person();
	console.dir(p.a);
</script>